一、Json简介
JSON官网(中文版)：http://www.json.org/json-zh.html
JSON(JavaScript Object Notation)是一种轻量级(轻量级？简单、易操作、快捷)的数据交换格式。主要目的就是给出一套通用的数据格式，大家按照这种格式定义自己的数据，方便数据的交换。特点是(相对来说)易于人阅读和编写，易于机器解析和生成。
Rules：
1.“名称/值”对的集合（A collection of name/value pairs）。不同的语言中，它被理解为对象（object），纪录（record），结构（struct），字典（dictionary），哈希表（hash table），有键列表（keyed list），或者关联数组 （associative array）。
2.值的有序列表（An ordered list of values）。在大部分语言中，它被理解为数组（array）。
JSON可以有以下格式：
1.对象是一个无序的“ ‘名称/值’ 对”集合。一个对象以“{”（左括号）开始，“}”（右括号）结束。每个“名称”后跟一个“:”（冒号）；“‘名称/值’ 对”之间使用“,”（逗号）分隔。
object的 名称 /值 结构
2.数组是值（value）的有序集合。一个数组以“[”（左中括号）开始，“]”（右中括号）结束。值之间使用“,”（逗号）分隔。
“值的类型”可以是哪些数据类型
以上是最基本的json知识，想深入了解的，请移步官网。
下面举个栗子给大家尝尝：
{
"type":"forecast1d",
"weatherinfo": [
{
"city": "北京",
"cityid": "1",
"temp1": "22℃",
"temp2": "10℃",
"weather": "晴",
"ptime": "11:00"
},
{
"city": "上海",
"cityid": "2",
"temp1": "24℃",
"temp2": "12℃",
"weather": "晴",
"ptime": "11:00"
}
]
}
栗子好难看，上截图(截图太小看不清...戳这里看大图<-- !)：
一个简单的JSON串
NOTE：左侧为JSON字符串，右侧为解析结构，方便查看。
福利：截图是我在一个在线JSON Editor上截的，体验一下-->JSON Editor，很好用推荐给大家。
二、使用Gson在Android中解析Json
认清了JSON，就要解析它。
你可以使用的JSON库：
JSONObject(源自Android官方)、
GSon(源自Google)、
Jackson(第三方开源库)、
FastJSON(第三方开源库)、
等。。。
本篇文章使用Gson解析JSON，Gson地址：http://code.google.com/p/google-gson/
google-gson
无法下载？百度云分享一下http://pan.baidu.com/s/1kTur5xd,提取密码:5oae
根据JSON串的结构定义一个类(这里我们把这个类叫Result)，我们直接把得到的JSON串解析成这个类。class Result定义如下：
import java.util.List;
public class Result {
public String type;
public List
weatherinfo;
public static class Info {
public String city;
public String cityid;
public String temp1;
public String temp2;
public String weather;
public String ptime;
}
}
class Result
定义好了待解析成的class之后，接下来使用Gson解析JSON串就可以了：
Gson gson = new Gson();
Result r = gson.fromJson(jsonData, Result.class);
So easy！
难点：1.如何定义这个待解析成的类？其实很简单，看到JSON结构里面有{ }你就定义一个类，看到[ ]你就定义一个List即可，最后只剩下最简单的如String、int等基本类型直接定义就好。2.内部嵌套的类，请使用public static class className { }。3.类内部的属性名，必须与JSON串里面的Key名称保持一致。这三点请自行对照我们上面举的Result的栗子，都有对应。
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"date":"2016-03-24","hum":"10","pcpn":"0.0","pop":"0","pres":"1029","tmp":{"max":"16","min":"3"},"vis":"10","wind":{"deg":"285","dir":"无持续风向","sc":"微风","spd":"4"}
}
],
"hourly_forecast":[
{"date":"2016-03-18 10:00","hum":"22","pop":"0","pres":"1014","tmp":"18","wind":{"deg":"130","dir":"东南风","sc":"微风","spd":"13"}},
{"date":"2016-03-18 13:00","hum":"12","pop":"0","pres":"1014","tmp":"22","wind":{"deg":"39","dir":"东北风","sc":"微风","spd":"15"}},
{"date":"2016-03-18 16:00","hum":"12","pop":"0","pres":"1014","tmp":"22","wind":{"deg":"80","dir":"东风","sc":"3-4","spd":"17"}},
{"date":"2016-03-18 19:00","hum":"19","pop":"0","pres":"1016","tmp":"18","wind":{"deg":"75","dir":"东北风","sc":"微风","spd":"14"}},
{"date":"2016-03-18 22:00","hum":"27","pop":"0","pres":"1019","tmp":"14","wind":{"deg":"40","dir":"东北风","sc":"微风","spd":"11"}}
],
"now":
{
"cond":{
"code":"502",
"txt":"霾"},
"fl":"6",
"hum":"45",
"pcpn":"0",
"pres":"1011",
"tmp":"13",
"vis":"3",
"wind":{"deg":"350","dir":"东北风","sc":"4-5","spd":"18"}
},
"status":"ok",
"suggestion":
{
"comf":{"brf":"舒适","txt":"白天不太热也不太冷，风力不大，相信您在这样的天气条件下，应会感到比较清爽和舒适。"},
"cw":{"brf":"不宜","txt":"不宜洗车，未来24小时内有霾，如果在此期间洗车，会弄脏您的爱车。"},
"drsg":{"brf":"较冷","txt":"建议着大衣、呢外套加毛衣、卫衣等服装。体弱者宜着厚外套、厚毛衣。因昼夜温差较大，注意增减衣服。"},
"flu":{"brf":"易发","txt":"昼夜温差大，且空气湿度较大，易发生感冒，请注意适当增减衣服，加强自我防护避免感冒。"},
"sport":{"brf":"较不宜","txt":"有扬沙或浮尘，建议适当停止户外运动，选择在室内进行运动，以避免吸入更多沙尘，有损健康。"},
"trav":{"brf":"较不宜","txt":"空气质量差，不适宜旅游"},
"uv":{"brf":"最弱","txt":"属弱紫外线辐射天气，无需特别防护。若长期在户外，建议涂擦SPF在8-12之间的防晒护肤品。"}
}
}
]
}
[{"aqi":
{"city":
{"aqi":"378","co":"2","no2":"96","o3":"19","pm10":"259","pm25":"327",
"qlty":"严重污染","so2":"23"
}
},"basic":{
"city":"北京","cnty":"中国","id":"CN101010100","lat":"39.904000","lon":"116.391000",
"update":{"loc":"2016-03-18 09:48","utc":"2016-03-18 01:48"}
},
"daily_forecast":[
{"astro":{"sr":"06:20","ss":"18:24"},
"cond":{"code_d":"502","code_n":"101","txt_d":"霾","txt_n":"多云"},
"date":"2016-03-18","hum":"11","pcpn":"0.0","pop":"0","pres":"1013","tmp":{"max":"21","min":"5"},"vis":"10","wind":{"deg":"47","dir":"无持续风向","sc":"微风","spd":"5"}},{"astro":{"sr":"06:18","ss":"18:25"},"cond":{"code_d":"101","code_n":"104","txt_d":"多云","txt_n":"阴"},
"date":"2016-03-19","hum":"22","pcpn":"0.0","pop":"0","pres":"1023","tmp":{"max":"15","min":"4"},"vis":"10","wind":{"deg":"176","dir":"无持续风向","sc":"微风","spd":"2"}},{"astro":{"sr":"06:17","ss":"18:26"},"cond":{"code_d":"104","code_n":"101","txt_d":"阴","txt_n":"多云"},
"date":"2016-03-20","hum":"24","pcpn":"0.0","pop":"0","pres":"1027","tmp":{"max":"16","min":"4"},"vis":"10","wind":{"deg":"159","dir":"无持续风向","sc":"微风","spd":"3"}},{"astro":{"sr":"06:15","ss":"18:27"},"cond":{"code_d":"101","code_n":"101","txt_d":"多云","txt_n":"多云"},
"date":"2016-03-21","hum":"21","pcpn":"0.0","pop":"12","pres":"1021","tmp":{"max":"17","min":"5"},"vis":"10","wind":{"deg":"209","dir":"无持续风向","sc":"微风","spd":"0"}},{"astro":{"sr":"06:13","ss":"18:28"},"cond":{"code_d":"101","code_n":"101","txt_d":"多云","txt_n":"多云"},
"date":"2016-03-22","hum":"27","pcpn":"0.0","pop":"46","pres":"1024","tmp":{"max":"18","min":"6"},"vis":"10","wind":{"deg":"124","dir":"无持续风向","sc":"微风","spd":"6"}},{"astro":{"sr":"06:12","ss":"18:29"},"cond":{"code_d":"101","code_n":"100","txt_d":"多云","txt_n":"晴"},
"date":"2016-03-23","hum":"10","pcpn":"0.0","pop":"34","pres":"1031","tmp":{"max":"15","min":"4"},"vis":"10","wind":{"deg":"336","dir":"无持续风向","sc":"微风","spd":"2"}},{"astro":{"sr":"06:10","ss":"18:30"},"cond":{"code_d"